Alvar is originally a Swedish name and thus it became first popular among the Swedish-speaking Finns.
Alvar is one of those "vintage trendy" names: it was popular from the 1900's to the 1930's and has its revival now in the 2010's, appearing on the last year's top 50 first names' list. The most famous bearer is architect and designer
Alvar Aalto (1898-1976): almost every
Finn owns a piece of furniture, textiles or glassware designed by him, which has probably influenced on
Alvar's popularity.
Hilla is a fairly modern name as it became more common in the 1980's/1990's. Like I mentioned in the original post, Hilla means "cloudberry" in Finnish, but Hilla has also been used as a nickname for "Hil-" starting names such as
Hilda,
Hilja and Hilkka. I don't know any famous Hillas, but I've had a couple of classmates bearing this name.
As it's told in the BtN's database,
Terhi originates from the Finnish mythology: Terhenetär was a sprite associated with mist, and the (archaic) word "terhen" means "mist". Neither Terhenetär or Terhen are used on ordinary people (as they're too mythological), but
Terhi is quite a common name. Most Terhis were born in the 1960's-1990's, so it's a bit dated. There are many famous Terhis in Finland, but none of them is really known abroad. There has currently been buzz about singer
Terhi Kokkonen, who was supposed to take part in a popular TV show "Vain Elämää", but she left the show when they were still recording it.
This message was edited 4/8/2018, 3:56 AM